Re: GVP IO-Extender

[Ken T. <ke...@we...>]

On Thu, 21 Mar 2002, Geert Uytterhoeven wrote:

> On Thu, 21 Mar 2002, Ken Tyler wrote:

> Do not allow the module to be unloaded?

OK, I'll look at that but read on...
 
> BTW, how does AmigaOS handle this? Or are you always out-of-luck if you ever
> used the IO-Ext parport under AmigaOS and booted into Linux afterwards?

Booting into linux is OK for a one piece kernel as any interrupt will be
handled. A modular kernel dies if an interrupt occurs before the module is
loaded (or after it is unloaded).  

The 16c552 chip on the IO Extender has seperate interrupt enables for the
parallel and two serial ports. The 16c552 also has an interrupt mode
control input (GVP_IRQ_ENA in the 2.2 includes) which turns PC/AT mode on
and off, pretty sure this only affects the parallel port.

Turning off the the chip parallel port interrupt enable looks like it
causes continuous interrupts. This is what the 2.2.n comments suggest.

The safe way to use the Extender is not to use it as a module.

Or if it is a module the parallel port interrupt (GVP_IRQ_ENA) needs to be
shut up when linux boots.

Ken.